Method of casting



Patented Feb. 8, 1949 L oFFlcr;

METHOD .0F CASTING John Gombosnnmburgnra; ,l

Application ctobcr 21, 1944, Serial vNo. 559,763 y 4 claims. (ci. zz-zos) This invention relates to metal founding, and more particularly the casting of large metal bodies such, for example, as rolling millrolls, ingots, and other large bodies where piping has heretofore been a detrimental factor.

In the casting of large bodies of metal, it is well known that the outside solidies before the center, and that'portions of small sections usually solidify before portions of large section. The solidification of the exterior of the body followed by the cooling and shrinking of the molten interior, results in the formation of a cavity or pipe in the upper end of the casting which may extend an indeterminate depth into the body of the metal. Moreover, the solidiiication of the metal may be such as to set up strains, especially in the casting of objects such as rolling mill rolls, tending to cause the neck of the roll to a'said mold contained not shown, and which has a cavity 3 conforming break at a point intermediate its length.- This breakage is usually manifested by a convex surface on the kstump of the roll neck that remains attached to the roll body.

The present invention provides a mold and a method of casting which substantially reduces, and to a large extent, eliminates such conditions. The invention contemplates a method of procedure in which the mold is filled with hot metal to a point of overflowing, whereby dross and im,- purities that often oat on the top of the metal are oated outside of the mold cavity. After the mold has been filled to this extent, a ,separating disc, is placed in position on top, of the molten metal and then further metal is oated into means providing a'reservoir in the upper part of the mold cavity. The function of the reservoir is firstly, to provide a body of hot'metal that will retard the cooling of the upper part of the casting, and secondly, to cover the disc and provide a pressure downwardly against the disc. If a -pipe tends to form, it forms first in this auxiliary body of metal. It may extend down to the disc, and thereit will be interrupted by the disc, and can extend no lower. As shrinkage of the metal occurs under the surface of the disc, the disc will move or -be pressed down and to some ex- 1 tent, hot metal above the disc may flow around its edges to the body of the casting below. Whatever theexact mechanism, the disc or separator serves to eliminate pipe below it.

The invention may be more fully understood by reference to the accompanying drawings, in which:

Fig. 1 represents a longitudinal, vertical section through a mold for casting, a rolling mill roll, said mold embodying my invention; and

Fig. 2 shows the application of my invention to a conventional ingot'mold which may be either a bottom pour or a top pour mold, but is preferably a bottom pour mold.

v4Referring first to the drawings, 2 designates to the roll to be cast. At the lower end is a portion I forming a neck at one end of the roll.-

At the top of the cavity 3 there is a built-up extension 5 to form the other neck of the. roll, this extension 5 being spaced from the exterior of thernold body, thereby providing an annular trough around the extension 5, the body 2 of the mold projecting a substantial distance above the extension 5. tapered exteriorly toward its base.

In using the mold, hot metal is poured in the usual manner into the mold cavity through the top thereof until the extension 5 has been filled, and the pouring is then continued to float the dross and impurities overthe top of the extension 5 into the annular trough t, part of the process has been performed, a separating d isc 1 of a. size to loosely fit into the extension 5 is placed in the top of the extension. The separating disc may be either of metal or refractory, metal having a higher melting point than the metal in the mold preferably being used. The'separator will preferably be such that tend to float on top of the molten metal in the vbefore the additional metal is added.

extension 5, in which case heavy restraining elements 8 may be placed over the top of the plate, lf the plate is heavier, and in order'to assure that the separator will not sink to the bottom, the'inf terlor of the upper part of the extension 5 may be countersunk and the separator be of a diameter such that should it sink, it could not pass belojw v the shoulder 8 at the bottom of this enlarged or countersunk portion, It may be noted that in practice thel cold metal separator, when placed atwise on the molten metal, does not sink. After the disc is in place. more molten metal is poured into the top of the mold to completely fill the cavity 6 and cover the separator to a depth of vseveral inches.

After this has been done, the casting is allowed to cool. The body of metal in the channel B keeps the narrow section of metal forming the y upper roll neck hot, so that it does not solidify rapidly. The head of metal above the disc yI presses down on the disc so that as shrinkage occurs in the casting comprising4 the roll, the

disc moves down, tending to keep the end of thecasting even. Ifa pipe starts to form, it will form in 'the metal above the disc 3 because the pipe forms from the outside of the molten mass toward its center. Any opening that thusv tends to develop may reach the separator plate but there can be no continuity of that opening below the separator. There will be no formation of any secondary pipe below the separator because of the downward pressure of the 'separator against the metal, and because the pipe starts at within a suitable casing:

The extension 5 is preferably v After this the exterior and not internally. The disc 1 is suiiiciently loose so that gases can escape around it, and so that molten metal may ow around the edges into the part of the cavity below the separator.

Fig. 2 illustrates the application of my invention to the casting of ingots wherein I designates a conventional ingot mold, preferably a bottom pour mold. Set into the upper portion f this mold belowthe top thereof is a frustoonical pressed metalv shell Il which may be either irictionallyv held in the mold cavity, or the mold cavity may be provided with a recess or shoulder forsupporting it. It has an open center designated l2. As shown in Fig. 2, it is set into the mold cavity so that it slopes upwardly and inwardly.

In operation, hot metal is charged into the mold cavity until it overilows through the openy ing I2, allowing thedross and impurities to overflow into the annular trough I3 provided around the exterior of the body II, and the interior of the mold. A separator plate I4 is then set in the hole I 2 and more metal is poured into the top of the mold to a height of several inches above the separator.

Thus there is provided a condition similar tc that described in connection with Fig. 1, in which there is an annular body of molten metal' I3 around the upper part of the ingot with an overlying body of metal pressing down on the disc Il.

shrinkage which tends to occur below the separator I4 causes the separator to move downwardly, and there is a convex body of metal under the member II, instead of a concave body which is usually present in a cooling ingot. The separator may be supported against premature sinking by means of lugs or hooks I5 formed on the edge of the separator, and which contact the top of the cone if the separator sinks too far, 'these hooks normally being suiciently above the top of the 4 my invention and under the scope o! the following l claims.

I claim:

1. The method of casting metal objects in a mold wherein the mold has a vertical depth greater than the depth of the object to be formed and has an annular trough adapted to surround the upper part of the body to be formed, which comprises lling the mold cavity to .a point where dross and impurities. overilow from the mold cavity into said annular trough, substantially covering the trough of the metal casting to the mold cavity with a separator plate and then lilling molten metal into the top of the mold to fill the annular trough and cover the separator plate so as to provide a depth of molten -metal above the separator plate.

2. The method of casting large metal bodies which comprises forming the top of the mold cavity in which the body is to be cast with a portion of reduced cross sectional area, the portion of reduced area being surrounded by a trough for receiving the metal, iilling the mold cavity with molten metal and overowing dross and impurities 4into said annular trough, interrupting the pouring operation and placing a separator of reduced area being surrounded by a trough disc to let it move down several inches. Prefer-1 ably, the separator oats on the metal and is restrained in place by heavier or non-floating elements I5'.

From both of the embodiments herein described, it will be seen that the invention comprises a method and Yapparatus for casting wherein there is a hot body of metal above the principal part of the casting with an intervening separator, the overlying body of metal pressing down on the separator, and also providing a trough to retard the cooling of the upper part of the body of metal being cast. It will also be seen that in both embodiments which are merely typical of various embodiments of my invention, provision is made for the cleaning of the principal mold cavity of dross and impurities by overilowing them from the mold cavity before the separator plate is put into place. It will be understood that the metal poured in above the separator is cropped oi the finished casting and -reused as scrap. It may-be pointed out that in of Fig. 2 might be sand.

While I have illustrated and described certain specific embodiments of my invention, itv will be understood that these are merely by way of illus. tration, and that various changes and modifications may be made Within the contemplation of for receiving the metal, iilling the mold cavity with molten metal and overflowing dross and impurities into said annular trough, interrupting the pouring operation and placing a separator plate on top of the cast metal in the mold cavity, and then filling the vtrough and the mold cavity above the separator plate with molten metal, the separator plate being adapted to oat on the molten metal.

4. The method ef fisting large merel bodies which comprises forming the top of the mold cavity in which the body is to be cast with a portion of reduced cross sectional area, the portion of reduced area being surrounded by a trough for receiving the metal, filling the mold cavity with molten metal and overflowing dross and impurities into said annular trough, interrupting the pouring operation and placing a separator plate on top of the cast metal in the mold cavity, and then filling the trough and the mold cavity above the separator plate with molten metal, the separator plate bein-g adapted to oat on the molten metal, and restraining the separator from iloating to the top of the overlying body of metal.

JOHN GoMBosH.

REFERENCES CITED The following references are of record in -th file of this patent:

UNITED STATES PATENTS 

